Glucose induces β-cell apoptosis via upregulation of the Fas receptor in human islets

In autoimmune type 1 diabetes, Fas-to-Fas-ligand (FasL) interaction may represent one of the essential pro-apoptotic pathways leading to a loss of pancreatic beta -cells. In the advanced stages of type 2 diabetes, a decline in beta -cell mass is also observed, but its mechanism is not known. Human islets normally express FasL but not the Fas receptor. We observed upregulation of Fas in beta -cells of type 2 diabetic patients relative to nondiabetic control subjects. In vitro exposure of islets from nondiabetic organ donors to high glucose levels induced Fas expression, caspase-8 and -3 activation, and beta -cell apoptosis. The effect of glucose was blocked by an antagonistic anti-Fas antibody, indicating that glucose-induced apoptosis is due to interaction between the constitutively expressed FasL and the upregulated Fas. These results support a new role for glucose in regulating Fas expression in human beta -cells. Upregulation of the Fas receptor by elevated glucose levels may contribute to beta -cell destruction by the constitutively expressed FasL, independent of an autoimmune reaction, thus providing a link between type 1 and type 2 diabetes.